WWI Games:
Over the Top (Learn about trenches): http://www.warmuseum.ca/cwm/games/overtop/index_e.shtml

Vocabulary Game: http://www.neok12.com/vocabulary/World-War-I-01.htm

Jigsaw Puzzles: http://www.neok12.com/jigsaw-puzzles/World-War-I.htm

Slide Puzzles: http://www.neok12.com/slide-puzzles/World-War-I.htm (Uses same pictures as jigsaw puzzles.)

Label the Map of Europe (Interactive): http://www.neok12.com/diagram/World-War-I-01.htm

WWI When?: http://www.bbc.co.uk/schools/worldwarone/hq/worldwarwhen.shtml (Tough game - you need to know your history!)